1. Technical Field
This disclosure relates to the removal of peroxides from a naphtha stream or supply that has been exposed to oxygen. When exposed to oxygen, naphtha compounds can form peroxides which readily decompose to free radicals. This disclosure provides a reactor and a method for the catalytic conversion of such peroxides to useful hydrocarbons and oxygen which can be used to replace a conventional oxygen stripper column and conventional oxygen stripping method.
2. Description of the Related Art
Naphtha (C6-C10 hydrocarbons) is generated from the distillation of petroleum as well as coal, tar and shale oil and is a primary constituent of gasoline. Prior to being incorporated into a gasoline formulation, naphtha is typically hydrotreated or hydrodesulfurized.
Hydrotreating or hydrodesulfurization (HDS) is a common process to remove contaminates such as sulfur, hydrogen, condensed ring aromatics and/or metals in a catalytic process. However, prior to passing naphtha through a hydrotreating unit, naphtha often comes into contact with oxygen, either in storage or during transit. The oxygen reacts with naphtha to form peroxides, which readily decompose into free radicals. Once decomposed, the free radicals initiate the formation of oligomers (gums), which can result in fouling of the hydrotreating process unit.
Currently, such peroxides can be removed from a naphtha stream using a reboiled oxygen stripper column. The bottoms temperature of a conventional reboiled oxygen stripper column must be maintained at or above 176° C. (350° F.) to insure complete thermal decomposition of the peroxides. Thus, these conventional oxygen stripper columns have substantial energy consumption and therefore high operating costs. For example, a 28,750 BPSD oxygen stripper column requires approximately over $1.5 million in high-pressure steam per year to operate. Further, conventional oxygen stripper columns are relatively wide and therefore expensive to construct and consume a substantial footprint. For example, a typical oxygen stripper column and related equipment are very costly to construct.
As a result, some refiners bypass the oxygen stripping process altogether thereby adversely affecting the downstream naphtha hydrotreating unit. Specifically, some refiners consider it to be less expensive to incur the additional downtime for purposes of unfouling the naphtha hydrotreating unit rather than investing in an oxygen stripper column and incurring the additional capital and operating costs.
Therefore, there is a substantial need for an improved oxygen stripping process and equipment for naphtha streams that may be inexpensively incorporated into a refining process upstream of a naphtha hydrotreating unit.